1. Field of the Invention
The present invention relates to an extracorporeal blood circulation system for treating inflammatory diseases. More particularly, the present invention is concerned with an extracorporeal blood circulation system for treating inflammatory diseases, which has a construction such that, when extracorporeal blood circulation is conducted using the system with respect to blood from a patient, the system is capable of providing treated blood in which platelets are activated to a specific degree. By the use of the extracorporeal blood circulation system of the present invention, a high therapeutic effect on inflammatory diseases can be achieved, as compared to a therapeutic effect achieved by conventional extracorporeal blood circulation therapies (such as plasmapheresis and a method using a leukocyte trapping filter).
2. Prior Art
An inflammatory disease is a disease in which an infiltration of leukocytes into a diseased site occurs, or a disease in which an inflammation markedly occurs due to active oxygen and various cytokines which are released from leukocytes.
Ulcerative colitis and Crohn's disease are chronic inflammatory diseases of the digestive tract. Currently, ulcerative colitis is generally believed to be a cryptogenic disease; however, it has been suspected that ulcerative colitis is attributable to an antilarge intestine antibody, an autoimmune T cell and the like.
Methods for treating these diseases can be classified into internal-medical treatment and surgical treatment. In an internal-medical treatment, drugs are used for the treatment, wherein such drugs are appropriately selected in accordance with the degree of seriousness of the symptoms and the location of the ulcer. Examples of such drugs include salazosulfapyridine (manufactured and sold by The Green Cross Corporation, Japan), prednisolone (manufactured and sold by Shionogi & Co., Ltd., Japan), azathioprine (manufactured and sold by Sumitomo Pharmaceuticals Co., Ltd., Japan and Nippon Wellcome K. K., Japan) and tranilast (manufactured and sold by KISSEI PHARMACEUTICAL CO., LTD., Japan). Such internal-medical treatments are effective for most cases of ulcerative colitis; however, the use of a drug for treating ulcerative colitis poses the danger of the occurrence of a side effect.
In a surgical treatment, excision of the diseased site is performed by a surgical operation. However, with respect to Crohn's disease, after the excision, the probability of the recurrence of the disease is high. Further, with respect to both of ulcerative colitis and Crohn's disease, after the excision, it is frequently necessary that the patient be fitted with an artificial anus, inevitably leading to a lowering of the quality of life (QOL).
Articular rheumatism is a cryptogenic generalized inflammatory disease in which the cardinal symptom is polyarthritis, and which may also exhibit various extra-articular symptoms, such as subcutaneous nodule, angiitis, pleurisy and diffuse interstitial pneumonia. It has been known that an autoantibody, which is called a rheumatoid factor, is present in serum and synovia from a patient suffering from articular rheumatism.
For treating this disease (articular rheumatism), various drugs are used in combination, wherein such drugs are selected from, for example, a non-steroidal anti-inflammatory drug, a steroidal drug, an immunosuppressant and an immunomodulator. A treatment using drugs is effective for most patients suffering from articular rheumatism; however, this treatment poses the danger of the occurrence of a side effect. With respect to inflammatory diseases which do not favorably respond to any drug or which cannot be treated with drugs due to serious side effects of the drugs, it has been reported that such inflammatory diseases have been effectively treated by using plasmapheresis, such as double filtration plasmapheresis and immunoadsorption plasmapheresis. Plasmapheresis is a therapeutic method in which a rheumatoid factor and an immune complex, both which are thought to be causative of inflammation, are removed from the patient. {With respect to plasmapheresis, reference can be made to, for example, the following literature: Y. Itakura et al., Effects of Double Filtration Plasmapheresis for Rheumatoid Arthritis, p.133-136, Therapeutic Plasmapheresis (VII), Proceedings of the Seventh Symposium on Therapeutic Plasmapheresis, Tokyo, Jun. 5-6, 1987, Japanese Society for Therapeutic Plasmapheresis; N. Kobayashi et al., Plasma Cleaning Using Immunoadsorbent IM-P for Patients with Rheumatoid Arthritis, p.153-157, Therapeutic Plasmapheresis (IV), Proceedings of the 4th Symposium on Therapeutic Plasmapheresis, Tokyo, Jun. 2nd, 1984, Japanese Society for Therapeutic Plasmapheresis. } However, the convntional techniques of plasmapheresis are unsatisfactory in therapeutic effect. It is desired to improve the therapeutic effect of plasmapheresis.
In recent years, it has been suggested that inflammatory diseases (such as ulcerative colitis and articular rheumatism) can be treated by reducing the number of leukocytes present in the blood of a patient, using a device comprising a fibrous filter (see European Patent Application Publication No. 478,914, Pall Corporation). Further, there is also a report that, when a patient suffering from articular rheumatism was subjected to a lymphocyte removal therapy, the symptoms of the patient were alleviated (Artificial Organs, Vol. 15, No. 3, 1991).
However, the alleviation of clinical symptoms accompanying inflammatory diseases, which can be achieved by an extracorporeal blood circulation using a known leukocyte trapping filter, is at best similar to that obtained by plasmapheresis. Therefore, it is desired to improve the therapeutic effect of the extracorporeal blood circulation therapy.